1. Field of the Invention and more particularly, to miniature or subminiature rectangular potentiometers.
2. Prior Art
The size and cost of both active and passive components of electronic circuits have continued to decrease over the last few years. The cost and size of active electronic components and circuitry, such as, integrated circuits, have decreased to such an extent that a major fraction of the cost and space of a circuit is being assumed by other discrete components such as resistors, capacitors, potentiometers, and the like. The past years have witnessed an increasing effort to miniaturize and lower the cost of discrete components because of the cost and size limitations which these components have assumed with respect to overall electronic circuits.
The most difficult of all discrete components to miniaturize have been potentiometers. Numerous integrated circuit and thin film techniques exist by which capacitors and resistors may be miniaturized. Substantial effort has also been devoted to decrease the size and cost, and increase the reliability of discrete potentiometers. See, for example, U.S. Pat. No. 3,683,308 assigned to the same assignee of the present invention.
In many applications, a rectangular miniature potentiometer obtains size advantages over prior art square potentiometers. For example, rectangular potentiometers are typically employed in banks at the edge of a circuit card in order to facilitate adjustment of the circuitry on the card while the card is plugged into a chassis. The number of potentiometers which may be employed on any card or arranged along the edge of a card in a bank is limited by the geometrical configuration of the potentiometers. Clearly, long thin rectangular potentiometers are more adaptable to this type of application than sqaure potentiometers. However, such prior art potentiometers have tended to have complicated designs and to involve the assembly of a great number of exceedingly small parts. The tolerances of the parts involved becomes relatively large so that the accuracy and reliability of the finished potentiometer is diminished. Furthermore, prior art potentiometers have included positive stops which limit the rotation of the adjustment screw at the extreme settings of the potentiometer. Because of the small size of the components in a miniature potentiometer, the slightest rough handling or stress applied to the wiper against the stop could deform the wiper, destroy the operability of the potentiometer or impair its reliability. Therefore, what is needed is a highly reliable, small and low cost miniature rectangular potentiometer which at the same time is rugged.